The high cost of hearing aids is a major barrier underlying low treatment rates for hearing loss. Self-fitting of amplification can reduce the cost of service delivery and follow-up by allowing users to adjust amplification for their hearing needs and listening environments. The goal of this project is to determine the efficacy of self- fitting protocols by which users can (1) make initial adjustments to the electroacoustic and signal-processing characteristics of amplification and (2) modify those characteristics on the basis of experience, and in response to changing acoustic environments. The project involves interdisciplinary collaboration between audiologists, hearing scientists, and engineers. In the R21 phase, we will evaluate the efficacy of a self-adjustment protocol using a computer simulation with built-in sounds. Simultaneously, we will develop a system with ear-level assemblies and on-line speech processing capabilities. In the R33 phase, modifications to the self-fitting protocol will be evaluated, with the goal of optimizing outcomes while maintaining simplicity for independent operation by novice users. In parallel, engineering will incorporate the findings into a wearable device and add sound-input characterization and noise-management features. The sound-input characterization feature will collect and log sound-input data before, during and after user self-adjustment. Efficacy of the wearable system will be evaluated in the laboratory and in field studies: 1) to compare objective and subjective outcomes for self-adjusted and audiologist-adjusted settings, and 2) to evaluate self-adjustment patterns in everyday environments and determine the influence of acoustic input and user-related factors such as sound tolerance, personality, and working memory.